.\" -*- nroff -*-
.\" Copyright 2013 Los Alamos National Security, LLC. All rights reserved.
.\" Copyright 2010 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2007-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" $COPYRIGHT$
.TH MPI_Publish_name 3 "Jun 10, 2020" "4.0.4" "Open MPI"

.SH NAME
.nf
\fBMPI_Publish_name\fP \- Publishes a service name associated with a port

.fi
.SH SYNTAX
.ft R

.SH C Syntax
.nf
#include <mpi.h>
int MPI_Publish_name(const char *\fIservice_name\fP, MPI_Info \fIinfo\fP,
	const char *\fIport_name\fP)

.fi
.SH INPUT PARAMETERS
.ft R
.TP 1.4i
service_name
A service name (string).
.TP 1.4i
info
Options to the name service functions (handle).
.ft R
.TP 1.4i
port_name
A port name (string).

.SH OUTPUT PARAMETER
.TP 1.4i
IERROR
Fortran only: Error status (integer).

.SH DESCRIPTION
.ft R
This routine publishes the pair (\fIservice_name, port_name\fP) so that
an application may retrieve \fIport_name\fP by calling MPI_Lookup_name
with \fIservice_name\fP as an argument. It is an error to publish the same
\fIservice_name\fP twice, or to use a \fIport_name\fP argument that was
not previously opened by the calling process via a call to MPI_Open_port.

.SH INFO ARGUMENTS
The following keys for \fIinfo\fP are recognized:
.sp
.sp
.nf
Key                   Type      Description
---                   ----      -----------

ompi_global_scope     bool      If set to true, publish the name in
                                the global scope.  Publish in the local
                                scope otherwise.  See the NAME SCOPE
                                section for more details.

ompi_unique           bool      If set to true, return an error if the
                                specified service_name already exists.
                                Default to overwriting any pre-existing
                                value.
.fi

.sp
\fIbool\fP info keys are actually strings but are evaluated as
follows: if the string value is a number, it is converted to an
integer and cast to a boolean (meaning that zero integers are false
and non-zero values are true).  If the string value is
(case-insensitive) "yes" or "true", the boolean is true.  If the
string value is (case-insensitive) "no" or "false", the boolean is
false.  All other string values are unrecognized, and therefore false.
.PP
If no info key is provided, the function will first check to see if a
global server has been specified and is available. If so, then the
publish function will default to global scope first, followed by local. Otherwise,
the data will default to publish with local scope.

.SH NAME SCOPE
Open MPI supports two name scopes: \fIglobal\fP and \fIlocal\fP. Local scope will
place the specified service/port pair in a data store located on the
mpirun of the calling process' job. Thus, data published with local
scope will only be accessible to processes in jobs spawned by that
mpirun - e.g., processes in the calling process' job, or in jobs
spawned via MPI_Comm_spawn.
.sp
Global scope places the specified service/port pair in a data store
located on a central server that is accessible to all jobs running
in the cluster or environment. Thus, data published with global
scope can be accessed by multiple mpiruns and used for MPI_Comm_Connect
and MPI_Comm_accept between jobs.
.sp
Note that global scope operations require both the presence of the
central server and that the calling process be able to communicate
to that server. MPI_Publish_name will return an error if global
scope is specified and a global server is either not specified or
cannot be found.
.sp
Open MPI provides a server called \fIompi-server\fP to support global
scope operations. Please refer to its manual page for a more detailed
description of data store/lookup operations.
.sp
As an example of the impact of these scoping rules, consider the case
where a job has been started with
mpirun - call this job "job1". A process in job1 creates and publishes
a service/port pair using a local scope. Open MPI will store this
data in the data store within mpirun.
.sp
A process in job1 (perhaps the same as did the publish, or perhaps
some other process in the job) subsequently calls MPI_Comm_spawn to
start another job (call it "job2") under this mpirun. Since the two
jobs share a common mpirun, both jobs have access to local scope data. Hence,
a process in job2 can perform an MPI_Lookup_name with a local scope
to retrieve the information.
.sp
However, assume another user starts a job using mpirun - call
this job "job3". Because the service/port data published by job1 specified
local scope, processes in job3 cannot access that data. In contrast, if the
data had been published using global scope, then any process in job3 could
access the data, provided that mpirun was given knowledge of how to contact
the central server and the process could establish communication
with it.

.SH ERRORS
.ft R
Almost all MPI routines return an error value; C routines as
the value of the function and Fortran routines in the last argument. C++
functions do not return errors. If the default error handler is set to
MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
will be used to throw an MPI::Exception object.
.sp
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for
I/O function errors. The error handler may be changed with
MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN
may be used to cause error values to be returned. Note that MPI does not
guarantee that an MPI program can continue past an error.
.sp
See the MPI man page for a full list of MPI error codes.

.SH SEE ALSO
.ft R
.nf
MPI_Lookup_name
MPI_Open_port


